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O: Fachverband Oberflächenphysik
O 116: Wetting and Liquids at Interfaces and Surfaces II (joint session CPP/DY/O)
O 116.8: Vortrag
Freitag, 20. März 2020, 11:45–12:00, ZEU 260
Memory effects in polymer brushes showing co-nonsolvency effects — •Simon Schubotz1,2, Petra Uhlmann1, Andreas Fery1,2, Jens-Uwe Sommer1,2, and Günter K. Auernhammer1,3 — 1Leibniz-Institut für Polymerforschung Dresden e.V., 01069 Dresden, Germany — 2Technische Universität Dresden, 01069 Dresden, Germany — 3Max-Planck-Institut für Polymerforschung, 55128 Mainz, Germany
Some polymer brushes show a co-nonsolvency effect: They collapse in a mixture of two good solvents at some specific mixing ratio. Previous studies focused on the response of brushes which are entirely covered by a liquid. Here, we concentrate on partial wetting of co-nonsolvent polymer brushes, i.e., on the dynamics of a three-phase contact line moving over such brushes. We demonstrate that the wetting behavior depends on the wetting history of the polymer brush.
We use Poly(N-isopropylacrylamide) (PNiPAAm) brushes and water and ethanol as good solvents. In water/ethanol mixtures, the brush thickness is a non-monotonous function of the ethanol concentration. The memory of brushes is tested by consecutively depositing drops of increasing size at the same position. Previously deposited drops induce changes in the brush that modifies the wetting behavior (advancing contact angle) of subsequent drops.
We believe that the change in the contact angels is induced by adaptation like swelling of or liquid exchange in the brush due to the drop on top.